1. FIELD OF THE INVENTION
The present invention relates to a circuit interrupter in which an extinction of arc formed between contacts is carried out by puffing a gas for extinction.
2. DESCRIPTION OF THE PRIOR ART
When a gas having high extinction property such as SF.sub.6 is used in a circuit interrupter, it has been usual that certain gas pressure difference is caused by certain manner and the gas is puffed to the arc to result in the extinction of the arc whereby the current is interrupted.
Two manners have been proposed for forming the gas pressure difference. One is a double pressure system wherein the gas such as SF.sub.6 is charged at suitable pressure in a closed container and the gas pressure difference is given by forming high pressure by a separate gas pressure generator and the gas is puffed by opening a valve disposed between the higher pressure zone and the lower pressure zone at the interrupting time under interlocking to the interrupting operation whereby the extinction of the arc is attained. In the first system the gas pressure generator for generating and maintaining the high pressure gas and the structure for separating two pressure systems having higher pressure and lower pressure are complicated and large size so as to be uneconomical. Accordingly, it has been difficult to use it in practice from the viewpoint of the maintenance for maintaining the high gas pressure in the normal condition.
The other conventional system for forming the gas pressure difference is the single pressure type puffer system wherein a puffer device is operated in the gas space having several atm. charged in a closed container under interlocking to the interrupting operation and the resulting high pressure gas is puffed to the arc to interrupt the arc.
In the second system, the compressed gas having several atm. which is lower than that of the double pressure system, is charged, whereby the structure of the container is simple. However, the puffer device interlocking to the interrupting operation as the mechanical pressure generator is needed. The driving force for the puffer device is remarkably increased depending upon increasing the interrupting current and increasing the input power. Accordingly, in a large capacity type circuit interrupter, a driving device having high force is needed.
As a compensation means, an electromagnetic driving type puffer device has been proposed. However, they have disadvantages of large size, complicated structure and uneconomical and accordingly, it has been difficult to use in practice.